1. Field of the Invention
The present invention relates to a grinding machine which includes a nozzle for supplying grinding fluid or coolant to a grinding point where a grinding wheel contacts a workpiece. Hereinafter, “grinding fluid” represents each of the grinding fluid and the coolant.
2. Description of the Related Art
It is known for prior arts of a grinding machine shown in FIGS. 1(A) and 1(B), identified as first and second prior arts respectively. The grinding machine rotates a crankshaft W around the axis of a journal J of the crankshaft W, and grinds a revolving pin portion P of the crankshaft W by means of advancing/retracting a grinding wheel G adjusted to the eccentricity of the pin portion P by its revolution. Because of the revolution of the pin portion P corresponding to the rotational angle of the journal J, a grinding point K, where the grinding wheel G contacts the pin portion P, always moves according to the prior art of the grinding machine.
A nozzle 10 or 20 for supplying grinding fluid to the grinding point K is fixed on a wheel head 5 and advances/retracts therewith. The nozzle 10 shown in FIG. 4(A), called “straight-nozzle”, directly supplies the grinding fluid to the grinding point K of which pin portion P exists at the angle of 0 degree or 180 degrees across the direction of movement of the grinding wheel G at a right angle. The nozzle 20 shown in FIG. 4(B), called “right angle-nozzle”, supplies the grinding fluid to the surface of the grinding wheel G at a right angle upstream the grinding point K and pastes the fluid on the surface of the grinding wheel G. However, since the grinding point K moves as shown in FIGS. 4(A) and 4(B) by the revolving pin portion P, fixed straight-nozzle 10 or right angle-nozzle 20 hardly supplies enough grinding fluid to the moving grinding point K thereby to supply large quantities of the fluid thereto.
To resolve the above-mentioned problem, third prior art is proposed, Japanese Patent Laid Open No. 2000-108032 shown in FIG. 5, of which object is to supply the grinding fluid as small quantities as possible to the grinding point K and to cool down thereat efficiently. According to this prior art, two nozzles, the straight-nozzle 10 and the right angle-nozzle 20, are disposed on the wheel head 5 so that the nozzles 10, 20 advance/retract therewith. The straight-nozzle 10 directly supplies the grinding fluid to the grinding point K at which the grinding wheel G contacts the workpiece W, and the right angle-nozzle 20 supplies the grinding fluid to the surface of the grinding wheel G at a right angle upstream the grinding point K.
According to the third prior art, the wheel head 5 advances/retracts with both of the straight-nozzle 10 and the right angle-nozzle 20 in order to supply the grinding fluid as small quantities as possible. However, where the diameter of the grinding wheel G has become smaller because of its abrasion in relation to grinding, the grinding point K shifts so that the straight-nozzle 10 hardly supplies the grinding fluid thereto. Further, enough grinding fluid may not be supplied to the grinding point K by the straight-nozzle 10 because of the resistance of air flow following the surface of the grinding wheel G, unless the grinding fluid to be supplied is pressurized. Thus, a grinding fluid supply source has to become larger in order to supply large quantities of the grinding fluid or higher in pressure to pressurize the fluid to be supplied.
Further according to the third prior art, the right angle-nozzle 20 is mounted at a height in the machine to prevent the workpiece W or a jig from interfering, so that there exists a long distance between the grinding point K and the surface of the grinding wheel G where the grinding fluid is supplied. Therefore, large quantities of the grinding fluid are supplied to the grinding point K in order to compensate for insufficiency of the supply quantities relative to the position of the nozzle 20. Furthermore, bending the tip of the nozzle 20 at an angle of 90 degrees, the flow of the grinding fluid through the nozzle 20 falls into disorder so that the grinding fluid splashes radially at the opening of the nozzle 20 when the fluid has spouted. Thus, it costs to provide a facility to reduce the mist of the splashed grinding fluid. Moreover, since the grinding fluid spouts from the right angle-nozzle 20 to the abrasive surface of the grinding wheel G at a right angle, the rotation of the grinding wheel G is disturbed by right angle-fluid so as to increase torque of a motor attached to a spindle of the grinding wheel G.